Absorbent Article with Dual Core

ABSTRACT

An absorbent article. The absorbent article includes a topsheet having a body contacting surface, a backsheet joined to said topsheet, and an absorbent core disposed between the topsheet and the backsheet, wherein the absorbent core has an upper layer and a lower layer.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of, and claims priority under 35U.S.C. § 120 to, U.S. patent application Ser. No. 15/493,662, filed onApr. 21, 2017, which is a continuation of U.S. patent application Ser.No. 13/672,499, filed Nov. 8, 2012, now U.S. Pat. No. 9,649,228, issuedon May 16, 2017, which claims the benefit, under 35 USC § 119(e), ofU.S. Provisional Patent Application Ser. No. 61/557,723, filed on Nov.9, 2011, the entire disclosures of which are fully incorporated byreference herein.

FIELD OF INVENTION

This application relates to absorbent articles, such as sanitarynapkins, for the absorption of menses. More particularly, the presentinvention relates to absorbent articles utilizing multiple absorbentcores which have an improved comfort and fit.

BACKGROUND OF THE INVENTION

Unlike many types of disposable absorbent articles, absorbent articlessuch as pads and pantiliners are specifically designed to acquiremenstrual fluid. Menstrual fluid differs from other exudates, such asurine, in many important properties, such as viscosity. Therefore,absorbent articles should differ in their structural components fromdevices such as baby diapers to be optimized for the maximum absorptionof menstrual fluid.

For absorbent articles, the fluid insult has very differentcharacteristics, in the context of physio-chemical properties (e.g.,viscosity, fluid dynamics, etc.), volume, and time to be absorbed. Forexample, menstrual flow typically consists of two patterns. One of theseis “trickle” flow, which varies from 0.1 to 2 ml per hour. The secondpattern is “gush” flow which varies from a few ml in volume deliveredover a few seconds. Gush flow can result from an accumulation of mensespooling in the vagina which can then exit the body upon a change inposition, such as a transition from sitting to standing. In any event,even with gush flow, the total amount of fluid required to be absorbedinto the core in a given time is much less than that required by otherabsorbent products, such as baby diapers, for example. One practicalresult is that menstrual absorbent articles, rather than needing to bedesigned to handle gushing fluid, more typically handle fluid through a“blotting” effect. However, a need exists to be able to handleoccasional gush at the point of exit through improved absorption whereit is needed the most.

One possible method to improve absorbency is to increase the width orthickness of the absorbent article. However, this approach can representa less comfortable pad for the consumer. This is due to the relationshipbetween the body and the pudendal region. The body is naturally narrowin the front region and becomes broader towards the back. However, thepudendal region is found in the front and most of the discharge exitsthe body in the front region. This creates a tradeoff between comfortand increased protection.

Additionally, there is a continuing need for an absorbent article thathas improved body fit to better fit the body of the wearer while notsacrificing absorbency.

Additionally, there is a continuing need for providing guidance andassistance to consumers on how to place an absorbent article for betterbody fit and improved absorbency.

SUMMARY OF THE INVENTION

An absorbent article is disclosed. The absorbent article includes atopsheet having a body contacting surface and a lower surface oppositethe body contacting surface, a backsheet joined to the topsheet, and anabsorbent core disposed between the topsheet and the backsheet. Theabsorbent core has an upper layer comprising an upper surface and alower surface opposite the upper surface and a lower layer comprising anupper surface and a lower surface opposite the upper surface. The upperlayer includes an open celled foam and the lower layer includes afibrous network. The absorbent article has a transverse center line. Theabsorbent core upper layer perimeter comprises a longitudinal axis and atransverse axis center axis dividing the absorbent core upper layerperimeter into a section one and a section two. The upper layer sectionone has a surface area that is at least 5% greater than the surface areaof section two.

An absorbent article is further disclosed. The absorbent articleincludes a topsheet having a body contacting surface and a lower surfaceopposite the body contacting surface, a backsheet joined to thetopsheet, and an absorbent core disposed between the topsheet and thebacksheet, wherein the absorbent core comprises an upper layercomprising an upper surface and a lower surface opposite the uppersurface and a lower layer comprising an upper surface and a lowersurface opposite the upper surface. The absorbent article has atransverse center line. The absorbent core upper layer perimetercomprises a longitudinal axis and a transverse axis center axis dividingthe absorbent core upper layer perimeter into a section one and asection two. The upper layer section one has a surface area that is atleast 5% greater than the surface area of section two. The absorbentcore lower layer perimeter comprises a longitudinal axis and atransverse axis center axis dividing the absorbent core lower layerperimeter into a section one and a section two. The lower layer sectionone has a surface area that is at least 5% greater than the surface areaof section two.

BRIEF DESCRIPTION OF THE DRAWINGS

While the specification concludes with claims particularly pointing outand distinctly claiming the subject matter of the present invention, itis believed that the invention can be more readily understood from thefollowing description taken in connection with the accompanyingdrawings, in which:

FIG. 1 is a plan view of an absorbent article having an absorbent corehaving two separate layers where the top layer is asymmetric.

FIG. 1A is a plan view of the backsheet of an absorbent article.

FIG. 1B is a plan view of the absorbent core lower layer of an absorbentarticle having an absorbent core having two separate layers where thetop layer is asymmetrical.

FIG. 1C is a plan view of the absorbent core upper layer of an absorbentarticle having an absorbent core having two separate layers where thetop layer is asymmetrical.

FIG. 1D is a plan view of the topsheet of an absorbent article.

FIG. 2 is a cross section view of an absorbent article of the presentinvention, taken along the line 1-1 of FIG. 1.

FIG. 3 shows a schematic cross section of an absorbent core lower layeraccording to one embodiment of the present invention.

FIG. 4 is a plan view of an absorbent article having an absorbent corecontaining two separate layers wherein the top layer is discontinuous.

DETAILED DESCRIPTION OF THE INVENTION

As used herein, absorbent articles include pantiliners, catamenial pads,sanitary napkins, menstrual pads, and the like.

As used herein, the term “absorbent core” refers to the component of theabsorbent article that is primarily responsible for the liquid handlingproperties of the article, including acquiring, distributing, andstoring body liquids. As such, the absorbent core typically does notinclude the topsheet or backsheet of the absorbent article.

As used herein, the term “asymmetric” means having no symmetry about atleast one axis.

The terms “body-contacting surface” and “wearer-contacting surface” areused interchangeably herein and refer to one or more surfaces of anyarticle component that is intended to be worn or positioned toward oradjacent the body of the wearer/user for contact between the wearer/userand the article's surface at some time during the use period. The term“garment surface” as used herein refers to the outer or exterior surfaceof any article component that is intended to be worn or positionedadjacent a wearer's undergarments, or in the case of an absorbentarticle which is not worn by the user, the garment surface is typicallypositioned adjacent a user's hand or other implement assisting in theuse of the absorbent article. As used herein, the term “wearer” and“user” are used interchangeably as the present invention contemplatesabsorbent articles which may not be intended to be worn, but rather usedto absorb bodily exudates.

As used herein, the terms “body liquids,” “body fluids,” or “bodyexudates” include, but are not limited to menses, vaginal discharges,blood, sweat, and combinations of these substances.

As used herein, the term “flexible” refers to materials which arecompliant and readily conform to the general shape and contours of thewearer's body under normal body-imposed forces.

As used herein, the term “foam” is synonymous with the term “cellularpolymer,” which includes materials having a significant void volume,typically greater than 75%. “Open-celled” foams further have areticulated internal structure disposed therein comprising relativelythin “strut” elements interconnected and forming cells or poresproviding for fluid communication throughout the structure. Mean celldiameters refer to the diameter of the pores in the foam visible bymicroscopy. The pores tend to be relatively spherical in shape and themean diameter can be measured by using microscopic techniques. Onesuitable technique is to use a scanning electron micrograph and measurethe apparent mean diameter of at least 25 representative cells todetermine the mean. The density of foams can be determined usinguncompressed samples of said foams devoid of contaminants such as water,and measuring the volume and weight of the foam. A cubic sample havingan edge length greater than or equal to 2 cm is practical.

As used herein, “hydrophilic” refers to a material or substance havingaffinity for water or aqueous fluids. In general, a hydrophilic surfacewill have a contact angle with water of less than 60°, or even less than30°.

As used herein, the term “inorganic” refers to a material which is notorganic in nature. As used herein, the term “organic” refers tocompounds of carbon.

As used herein the term “joined” refers to the condition where a firstmember is attached, or connected, to a second member either directly orindirectly. Where the first member is attached, or connected, to anintermediate member which in turn is attached, or connected, to thesecond member, the first member and second member are joined indirectly.

As used herein, the term “layer” refers to a three dimensional structurehaving two dimensions that are substantially greater than the thirddimension. The term layer is not limited to single layers or sheets ofmaterial. Thus a layer may comprise laminates or combinations of severalsheets or webs of the requisite type of materials. Accordingly, the term“layer” includes the terms “layers” and “layered.”

As used herein, the term “lower layer” refers to the layer that servesto acquire gushes, control wicking of exudates, and/or store the fluid.A portion of the lower layer remains in close capillary contact with theupper layer. The lower layer can be referred to as a fluid storagelayer.

As used herein, the term “microfibers” refers to fibers having anaverage effective diameter of 0.1 micron to 6 microns and an aspectratio of at least 100. The aspect ratio of a microfiber is the contourlength of the fiber divided by the average effective diameter of thefiber. The contour length of a fiber is the length of the fiber in asubstantially straightened condition. Long microfibers can have aspectratios which exceed 1×10¹². The microfiber may be of any configuration,including but not limited to straight, curled, kinked, crimped, andcombinations thereof. The cross sectional area of the microfiberorthogonal to its contour length at any point may have any geometricshape, including but not limited to circular (round), square, flat,oval, star-shaped, irregular, and combinations thereof. For fibershaving a non-circular cross section, the effective diameter is thediameter of a circle having a cross sectional area equal to that of thefiber. Microfibers may comprise any material, including but not limitedto natural polymers, synthetic polymers, minerals, glass, ceramics,metals, vegetable matter, animal matter, carbon, and combinationsthereof. A sample of microfibers having an average effective diameterbetween 0.1 and 6 microns may contain individual fibers with diametersgreater than 6 microns and/or individual fibers with diameters less than0.1 micron.

“Non-biopersistent” refers to microfibers comprising at least 18%alkaline and alkaline earth oxides and meet at least one of the criteriafor lack of biopersistence listed below. A non-biopersistent materialaccording to the present invention can also meet the criteria of theGerman Dangerous Substances Ordinance (Gefahrstoffverordnung) Annex V,No. 7.1(1). A suitable method for selecting a fiber composition to testfor non-biopersistence of certain fibers according to the test methodbelow is to use the method reported by Eastes, W., Potter, R. M., andHadley, J. G. (2000), “Estimation of Dissolution Rate from In-VivoStudies of Synthetic Vitreous Fibers,”‘Inhalation Toxicology, 12(11),1037-1054. An online calculator implementing the method can be found athttp://fiberscience.owenscorning.com/kdisapp.html. This calculatorpredicts the rate of biodissolution as a function of the chemicalcomposition of the fiber. A non-biopersistent fiber meets at least oneof the following criteria: (1) a short-term biopersistence test byinhalation showing that the fibers longer than 20 um have a weightedhalf-life of less than 10 days (a suitable short-term biopersistencetest by inhalation is described in European Union protocol ECB/TM/26rev. 7), or (2) a short-term biopersistence test by intratrachealinstillation showing that the fibers longer than 20 um have a weightedhalf-life less than 40 days (a suitable short-term biopersistence testby intratracheal instillation is described in European Union protocolECB/TM/27 rev. 7), or (3) an appropriate intraperitoneal test showing noevidence of excess carcinogenicity (a suitable test for carcinogenicityof inorganic vitreous microfibers after intra peritoneal injection inrats is described in European Union protocol ECB/TM/18(97)), or (4) asuitable long-term inhalation test showing the absence of relevantpathogenicity or neoplastic changes (A suitable long-term inhalationtest is described in European Union protocol ECB/TM/17(97)). These testmethods are reported in European Commission Joint Research CentreInstitute for Health and Consumer Protection Unit: Toxicology andChemical Substances, European Chemicals Bureau (1999), “Methods for theDetermination of the Hazardous Properties for Human Health of Man MadeMineral Fibres (MMMF),” Report 18748, David M. Bernstein and Juan M.Riego Sintes Eds.

As used herein, the term “perimeter” refers to the outer limits of anarea defined by a grouping of one or more smaller items.

As used herein, the term “pudendal” refers to the externally visiblefemale genitalia.

As used herein, the term “superabsorbent” refers to a material capableof absorbing at least ten times its dry weight of a 0.9% saline solutionat 25° C. Superabsorbent polymers absorb fluid via an osmotic mechanismto form a gel. Superabsorbents may be particulates, fibers, foams,sheets, or other shapes.

As used herein, the term “symmetry” refers to an exact correspondence ofform and constituent configuration on opposite sides of a dividing lineor plane or about a center or an axis.

As used herein, the term “upper layer” refers to the layer which is incloser proximity to the body of the wearer of the article in use thanthe lower layer, such that the upper layer receives body fluids(menstrual fluid, blood, and the like) before the lower layer. The upperlayer can be referred to as a fluid acquisition layer.

As used herein, the term “vitreous” refers to a material which issubstantially non-crystalline in that the material comprises more than90% amorphous material. A vitreous material can comprise more than 99%amorphous material.

FIG. 1 shows a plan view of an absorbent article 10. The absorbentarticle can have four basic layers including a liquid imperviousbacksheet 16, an absorbent core lower layer 40, an absorbent core upperlayer 30, and a topsheet 14 joined to the backsheet. An absorbent core18 including the absorbent core lower layer 40 and absorbent core upperlayer 30 is disposed between the topsheet 14 and the backsheet 16. FIGS.1A-1D show each of the four basic layers individually: FIG. 1A shows thebacksheet 16, FIG. 1B shows the absorbent core lower layer 40, FIG. 1Cshows the absorbent core upper layer 30, and FIG. 1D shows the topsheet14.

The absorbent article 10 has a longitudinal axis L and a transverse axisT that meet at a central point C. The absorbent article 10 has a frontpoint F and a back point B. The transverse axis T is located by takingthe midpoint between the absorbent article 10 front point F and the backpoint B. The absorbent article 10 may also be provided with additionalfeatures commonly found in sanitary napkins, including “wings” or“flaps” 60 as is known in the art, and/or a fluid acquisition layerbetween the topsheet 14 and the absorbent core 18 to promote fluidtransport from the topsheet 14 to the absorbent core 18.

The topsheet 14 of a sanitary napkin can have various optionalcharacteristics, as is known in the art. For example, the topsheet 14can have channels embossed or other textured surfaces therein to directfluid flow. The topsheet 14 may also have apertures 24. Secondarytopsheets, often called acquisition and/or distribution layers, can bebonded to the topsheet. Various visual signals, indicia, or othermarkings can be added, for example by ink jet printing a the topsheetupper surface 32 or a topsheet lower surface 35, as well as on thesecondary topsheet, the absorbent core, or the backsheet. The topsheet14 of the absorbent article 10 may have a lotion composition 22 disposedonto at least the body-contacting surface 12 thereof.

The backsheet 16 can be any known or otherwise effective backsheetmaterial, provided that the backsheet prevents external leakage ofexudates absorbed and contained in the absorbent article. Flexiblematerials suitable for use as the backsheet include, but are not limitedto, woven and nonwoven materials, laminated tissue, polymeric films suchas thermoplastic films of polyethylene and/or polypropylene, compositematerials such as a film-coated nonwoven material, or combinationsthereof.

The absorbent core 18 includes more than one layer. Each layer has afront point and a back point. The absorbent core 18 may include anabsorbent core upper layer 30 and an absorbent core lower layer 40. Theabsorbent core may have two layers, as shown by the absorbent core upperlayer 30 and the absorbent core lower layer 40 in FIG. 1 or additionallayers, such as 3 layers or more. The absorbent core 18 may have a totalthickness of 0.8 mm to 18 mm at its thickest point and 0.8 mm to 15 mmat its thinnest point.

The upper layer 30 of the absorbent core 18 has a perimeter 66.Additionally, each layer of the absorbent core 18 may have alongitudinal and a transverse axis. The transverse axis T1 of theabsorbent core lower layer 40 may be different than the transverse axisT2 of the perimeter of the absorbent core upper layer 30 and theabsorbent article transverse axis T. The transverse axis T2 is locatedby taking the midpoint between the front portion and the back portionoutermost perimeter points of the upper layer 30. Similarly, thelongitudinal axis L1 of the absorbent core lower layer 40 may bedifferent than the longitudinal axis L2 of the perimeter of theabsorbent core upper layer 30 and the absorbent article longitudinalaxis L. L1 and T1 meet at a central point C1. L2 and T2 meet at CentralPoint C2.

The absorbent core 18 can have additional features in the upper layer30, the bottom layer 40, or both the upper and lower layer. Theadditional features are not deducted from the total area of theabsorbent core upper or lower layer when present. Absorbent core 18additional features may be encompassed in a portion of a layer and donot serve as a break in the perimeter of the layer. The absorbent core18 additional features may include slits, slots, apertures, and lateralstiffeners,

The absorbent core upper layer 30 or the absorbent core lower layer 40can have a plurality of laterally-oriented slots 72 having an averagegap width of at least 1 mm prior to use. Slots 72 are consideredlaterally oriented if they have a major vector component at thelongitudinal center line L that is perpendicular to the longitudinalcenter line. Slots 72 can be substantially parallel, generally linearslots that are each parallel to center line L, and, therefore, have novector component in the longitudinal direction. However, slots 72 canhave other configurations, including generally curved orientations.Absorbent core 18 may also have any number of holes 70. Absorbent core18 can have additional modifications and features to facilitate desiredbending and folding. For example, absorbent core 18 can have additionalslits, apertures, perforations, lines of weakness, lateral stiffeners,and the like. In particular, in one embodiment a line of weakness suchas perforations or a score line along at least a portion of thelongitudinal center line L can aid in proper formation of a raised humpor ridge along the center line.

As shown in FIG. 1, apertures 24 can serve the additional benefit ofcapturing fluid and fluid components that would otherwise tend to runoff of the absorbent article 10 and possibly soil the garments of thewearer. For example, if fluid were to run off toward the longitudinalend of the absorbent article 10 shown in FIG. 1, the portion 16 ofapertures 24 could intercept the fluid as it progressed, permitting arelatively unobstructed passage to an underlying absorbent core 18.These apertures 24 may also serve as indicia regarding the placement ofthe absorbent article 10 regarding the pudendal region and theundergarment.

FIG. 1B shows the absorbent core lower layer 40. The absorbent corelower layer 40 is approximately no greater than 25000 mm², 16000 mm²9000 mm², 4000 mm², 1000 mm², or even less total surface area on any onesurface, such as, for example approximately 2500 mm². Alternatively, theabsorbent core lower layer covers no greater than 95%, 90%, 85%, 80%,75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, 20%, 15%, 10% ofthe backsheet 16. As seen in FIG. 1b , the absorbent core lower layer 40is divided by T1 into lower layer section one 56 and lower layer sectiontwo 58. Lower layer section one 56 has a surface area that is at least5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 61%, up to100% greater than the surface area of lower layer section two 58.Alternatively, lower layer section one 56 may equal lower layer sectiontwo 58 in total surface area. T1 may overlay T and/or T2. The absorbentcore lower layer 40 may consist of any geometric shape commonly known.

The absorbent core lower layer 40 can have a fibrous network includingmicrofibers. One suitable microfiber is a non-biopersistent inorganicvitreous microfiber having an average effective diameter of between 0.1microns and 6 microns. Inorganic vitreous microfibers particularlyuseful have 18% or more of alkaline oxides and alkaline earth oxides andare non-biopersistent as described previously. Vitreous microfibers canexhibit good fluid handling properties, resiliency, softness, and lackof biopersistence. Inorganic compositions suitable for makingmicrofibers useful in the present invention are described in EuropeanPat. 1048625B, U.S. Pat. No. 6,261,335, and published U.S. Pat.Application No. 2003/0015003. Suitable non-biopersistent inorganicvitreous microfibers are available from Lauscha Fiber International,Summerville, S.C.

The absorbent core lower layer 40 may have at least 5% of superabsorbentpolymer.

The absorbent core lower layer 40 can be formed from any suitablematerials. Examples of such materials include multiple plies of crepedcellulose wadding, fluffed cellulose fibers, wood pulp fibers also knownas airfelt, textile fibers, a blend of fibers, a mass or batt of fibers,airlaid webs of fibers, a web of polymeric fibers, and a blend ofpolymeric fibers.

More typically, the absorbent lower core can be made by air-laying themixture of fibers and thermoplastic material. In general, air-laying canbe carried out by metering an airflow containing the fibers andthermoplastic material, in substantially dry condition, onto a typicallyhorizontally moving wire forming screen. Suitable systems and apparatusfor air-laying mixtures 10 of fibers and thermoplastic material aredisclosed in, for example, U.S. Pat. No. 4,157,724 (Persson), issuedJun. 12, 1979, and reissued Dec. 25, 1984 as Re. 31,775; U.S. Pat. No.4,278,113 (Persson), issued Jul. 14, 1981; U.S. Pat. No. 4,264,289(Day), issued Apr. 28, 1981; U.S. Pat. No. 4,352,649 (Jacobsen et al),issued Oct. 5, 1982; U.S. Pat. No. 4,353,687 (Hosier et al), issued Oct.12, 1982; U.S. Pat. No. 4,494,278 (Kroyer et al), issued Jan. 22, 1985;U.S. Pat. No. 4,627,806 (Johnson), issued Dec. 9, 1986; U.S. Pat. No.4,650,409 (Nistri et al), issued Mar. 17, 1987; and U.S. Pat. No.4,724,980 (Farley), issued Feb. 16, 1988.

Any suitable web forming techniques, including wet laying, which can besuitable for staple fibers, may be used to form a fibrous network havingvitreous microfiber staple feedstock. The steps of wet laying includesdispersing vitreous microfiber staple in an aqueous medium. Thedispersion is then laid down on a forming screen from a head box orother suitable distribution means, and the aqueous medium drains throughthe forming screen to form a nascent web, which is then dried and woundto form a rolled web of vitreous microfibers.

A binder can be added to the web to improve mechanical stability of theweb. The binder can be thermoplastic binder fibers or powder added tothe furnish when the vitreous microfibers are wet laid. The drying stepcan then be used to melt the binder thereby stabilizing the web. Thebinder can have a hydrophilic material. The binder can include only asingle thermoplastic material. The binder may include a bicomponentfiber having two thermoplastic materials in which one of the materialshas a melting point substantially higher than that of the other materialso as to preserve fiber integrity when the fiber is exposed to atemperature that causes flow of the thermoplastic material having alower melting point.

The binder can be a latex binder applied to the wet nascent web as acomponent of the furnish or after web formation. The latex binder canthen be cured in a drying step. The binder can be a polymeric solution(e.g., aqueous polyvinyl alcohol) sprayed on the web which is driedalong with the microfibers in the drying step. The binder can be abinding adhesive, such as a hot melt material sprayed on the dried webbefore the dried web is wound. The hot melt material can be a layer offiberized hot melt adhesive.

The binder can be a thermosetting wet strength resin applied as acomponent of the furnish or after formation of the web. For example, aspray application of KYMENE 557H, available from Hercules, Wilmington,Del., can increase the strength of a fibrous network having microfibers.If a small amount of cellulosic fibers such as fibers from theEucalyptus species of tree or crill or similarly classified material isincluded, additional wet strength materials known in the papermakingarts may be included as a component of the furnish or after webformation. Nonlimiting examples of such materials include and PAREZ 631NC available from Lanxess, Pittsburgh, Pa., and the aforementionedKYMENE 557H.

Because binders may affect the fluid handling properties of the web,only the minimum amount necessary to obtain sufficient mechanicalstrength should be used. For a thermoplastic binder, the level can bebetween 0.1% and 20%. Alternatively, the level for the thermoplasticbinder can be between 0.1% and 15%. For post formation binders, theadd-on to the dry web can be between 0.1% and 20% or even between 0.1%and 15%.

In addition to webs having binder fibers, other types of fibers may beincorporated into the web to enhance the wet strength and the finalstrength of the web. Suitable high surface area fibers include microfibrous cellulose, high surface area cellulosic fibers (e.g.,conventional cellulosic pulp fibers, particularly eucalyptus fibers,crosslinked cellulosic fibers, including those crosslinked withpolyacids such as citric or polyacrylic), and highly refined cellulosicfibers having Canadian Standard Freeness between 1 and 200 can beuseful. Fibers having Canadian Standard Freeness of between 40 to 100,referred to herein as “crill,” can also be useful.

A portion of the fibers in the web may also include synthetic polymericor semi-synthetic polymeric fibers. For example, synthetic fibers suchas polyester, polypropylene, and polyethylene may be used in relativelysmall amounts to provide additional strength to the structure.Semi-synthetic fibers, such as rayon, are also suitable. One suitablesynthetic fibrous material is CREATE-WL, a short staple (3 mm to 18 mm)polypropylene fiber having a length suitable for wet laying marketed byFiberVisions, Covington, Ga. Other types of synthetic fibers includethose termed “bicomponent” fibers wherein a portion of the fiber is ofone type and another portion is of another type, often in a coaxialarrangement. An example of a bicomponent fiber is a fiber having a coreof polyethylene and a sheath of polypropylene surrounding the core.Other synthetic fibers which may be included are nylon, polyolefins,polyacrylonitrile, polyesters, polyamide, polyaramid, polyacrylatesincluding both polyalkylacrylates and sodium polyacrylates,superabsorbent fibers, and the like. The quantity of such fibers dependson the desired final properties of the web. Alternatively, the fiberscan be used in an amount be between 1% and 25%. The fibers can be usedat a level between 1% and 15%. The fibers can be used at a level between1% and 10%.

The web may be airlaid directly after formation of the micro fibers bycollecting the fibers on a suitable forming device or by usingconventional airlaying techniques used for staple-length fibers. Ineither case, the web may be formed by a collection of fibers on aforaminous structure. A vacuum system underlying the foraminousstructure can aid in gathering the fibers into a web form. Airlaid websof this type can also use binders and other fibrous materials asdescribed above for wet laid webs.

The web can have a basis weight of between 40 g/m² and 350 g/m².Alternatively, the web can have a basis weight between 80 g/m² and 190g/m². Layers of the web may be stacked to achieve higher overall basisweights. The density of the web can be between 0.04 g/cc and 0.25 g/cc.Alternatively, the density of the web can be between 0.07 g/cc and 0.10g/cc. Micro fibers can include at least 10% of the fibrous assembly.

The absorbent core lower layer 40 can have a substrate layer, a layer ofabsorbent polymer material, and a layer of adhesive. The substrate layercan for example comprise a fibrous material.

As shown in FIG. 1C, the upper layer 30 of the absorbent core 18perimeter 66 is asymmetric about the perimeter 66 transverse center lineT2. As shown in FIG. 1C, the upper layer 30 of the absorbent core 18perimeter 66 can include one wholly continuous portion 62.

The absorbent core upper layer 30 perimeter 66 is approximately nogreater than 20000 mm², 16000 mm², 9000 mm², 4000 mm², 1000 mm², or evenless total surface area on any one surface, including, for exampleapproximately 12000 mm². Alternatively, no greater than 10%, 15%, 20%,25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 80%, 85%, 90%, 95%,100% of the absorbent core upper layer 30 perimeter 66 overlaps with theabsorbent core lower layer 40 upper surface 46. Additionally, theabsorbent core upper layer 30 may be covered by no greater than 95%,90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%,20%, 15%, 10% of the topsheet 14 lower surface 35, such as, for examplewhere the absorbent core upper layer 30 perimeter 66 overlaps with theabsorbent core lower layer 40.

The perimeter 66 of the absorbent core upper layer 30 is divided by atransverse axis T2 into upper layer section one 52 and upper layersection two 54. Upper layer section one 52 may have a surface area thatis at least 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, or up to100% greater than the surface area of section two 54. Upper layersection one 52 may be equal in total surface area to upper layer sectiontwo 54. The absorbent core upper layer 30 can be asymmetric about thetransverse center line T2 of the absorbent core upper layer perimeter66. The absorbent core upper layer 30 can be symmetric about theTransverse center line T2 of the absorbent core upper layer perimeter66. The transverse axis T2 of the perimeter 66 may overlap T1 and/or T.T2 may also be located 5 cm, 4 cm, 3 cm, 2 cm, 1 cm away from T or T1along the longitudinal center line L2 towards the front or back of theabsorbent article.

As shown in FIG. 1 and FIG. 4, the upper layer 30 of the absorbent core18 perimeter 66 may have a continuous portion 62 (as shown in FIG. 1) orof more than one discontinuous portion 64 (as shown in FIG. 4).

The absorbent core upper layer 30 can include open celled foam. Oneexemplary open-celled foam, High Internal Phase Emulsion (HIPE) foam, isproduced from the polymerization of the monomers including thecontinuous oil phase of a HIPE. HIPE foams may have one or more layers,and may be either homogeneous or heterogeneous polymeric open-celledfoams. Homogeneity and heterogeneity relate to distinct layers withinthe same HIPE foam, which are similar in the case of homogeneous HIPEfoams or which differ in the case of heterogeneous HIPE foams. Aheterogeneous HIPE foam may contain at least two distinct layers thatdiffer with regard to their chemical composition, physical properties,or both; for example layers may differ with regard to one or more offoam density, polymer composition, specific surface area, or pore size(also referred to as cell size). For example, for a HIPE foam if thedifference relates to pore size, the average pore size in each layer maydiffer by at least 20%, by at least 35%, and by at least 50%. In anotherexample, if the differences in the layers of a HIPE foam relate todensity, the densities of the layers may differ by at least 20%, by atleast 35%, and by at least 50%. For instance, if one layer of a HIPEfoam has a density of 0.020 g/cc, another layer may have a density of atleast 0.024 g/cc or less than 0.016 g/cc, in certain embodiments atleast 0.027 g/cc or less than 0.013 g/cc, and in still other embodimentsat least 0.030 g/cc or less than 0.010 g/cc. If the differences betweenthe layers are related to the chemical composition of the HIPE or HIPEfoam, the differences may reflect a relative amount difference in atleast one monomer component, for example by at least 20%, in certainembodiments by at least 35%, and in still further embodiments by atleast 50%. For instance, if one layer of a HIPE or HIPE foam is composedof 10% styrene in its formulation, another layer of the HIPE or HIPEfoam should be composed of at least 12%, and in certain embodiments ofat least 15% styrene.

The use of a foam absorbent core upper layer 30 that is smaller in totalsurface area than the absorbent core lower layer 40 provides a higherabsorbency area only where it is needed the most, rather than on theentire surface of the absorbent core lower layer 40. This enables costsavings since foam is only used where it makes the biggest performanceimpact. The use of a smaller absorbent core upper layer 30 may also actas a signal for improved placement. Traditionally, users use the wings60 center line to place the absorbent article on the undergarment. Thecreation of a visible absorbent core upper layer 30 that is smaller insurface area than the absorbent core lower layer 40 allows the consumerto use a different marker versus wings 60 to determine proper placement.For instance, placement in relationship to the body instead of theundergarment may be more intuitive to a user—she can place the absorbentarticle in the undergarment such that the absorbent core upper layer 30lines up with her pudendal region. Further, when wings 60 are notpresent on an absorbent article 10, it is even more important to rely onthe absorbent core upper layer 30 to enable correct placement.

A HIPE foam having separate layers formed from differing HIPEs, asexplained in more detail below, provides a HIPE foam with a range ofdesired performance characteristics. For example, a HIPE foam includinga first and second foam layer, wherein the first foam layer has arelatively larger pore or cell size, than the second layer, when used inan absorbent article may more quickly absorb incoming fluids than thesecond layer. By way of example when used in an absorbent articled thefirst foam layer may be layered over the second foam layer havingrelatively smaller pore sizes, as compared to the first foam layer,which exert more capillary pressure and drain the acquired fluid fromthe first foam layer, restoring the first foam layer's ability toacquire more fluid. HIPE foam pore sizes may range from 1 to 200 μm andin certain embodiments may be less than 100 μm. HIPE foams of thepresent invention having two major parallel surfaces may be from 0.5 to10 mm thick, and in certain embodiments 2 mm or more. The desiredthickness of a HIPE will depend on the materials used to form the HIPE,the speed at which a HIPE is deposited on a belt, and the intended useof the resulting HIPE foam. The HIPE foam may have a thickness of 0.8 mmto 3.5 mm.

The HIPE foams of the present invention are relatively open-celled. Thisrefers to the individual cells or pores of the HIPE foam being insubstantially unobstructed communication with adjoining cells. The cellsin such substantially open-celled HIPE foam structures haveintercellular openings or windows that are large enough to permit readyfluid transfer from one cell to another within the HIPE foam structure.For purpose of the present invention, a HIPE foam is considered“open-celled” if at least 80% of the cells in the HIPE foam that are atleast 1 μm in size are in fluid communication with at least oneadjoining cell.

In addition to being open-celled, in certain embodiments HIPE foams aresufficiently hydrophilic to permit the HIPE foam to absorb aqueousfluids, for example the internal surfaces of a HIPE foam may be renderedhydrophilic by residual hydrophilizing surfactants or salts left in theHIPE foam following polymerization, by selected post-polymerization HIPEfoam treatment procedures (as described hereafter), or combinations ofboth.

A HIPE foam can be flexible and exhibit an appropriate glass transitiontemperature (Tg). The Tg represents the midpoint of the transitionbetween the glassy and rubbery states of the polymer. In general, HIPEfoams that have a higher Tg than the temperature of use can be verystrong but will also be very rigid and potentially prone to fracture. Incertain embodiments, regions of the HIPE foams of the current inventionwhich exhibit either a relatively high Tg or excessive brittleness willbe discontinuous. Since these discontinuous regions will also generallyexhibit high strength, they can be prepared at lower densities withoutcompromising the overall strength of the HIPE foam.

HIPE foams intended for applications requiring flexibility shouldcontain at least one continuous region having a Tg as low as possible,so long as the overall HIPE foam has acceptable strength at in-usetemperatures. In certain embodiments, the Tg of this region will be lessthan 30° C. for foams used at ambient temperature conditions, in certainother embodiments less than 20° C. For HIPE foams used in applicationswherein the use temperature is higher or lower than ambient, the Tg ofthe continuous region may be no more than 10° C. greater than the usetemperature, in certain embodiments the same as use temperature, and infurther embodiments 10° C. less than use temperature wherein flexibilityis desired. Accordingly, monomers are selected as much as possible thatprovide corresponding polymers having lower Tg's.

The mean cell diameters for open-celled foams can be between 10 and1,000 microns. The mean densities of open-celled foams can be between 40kg/m3 and 100 kg/m3. The ability of a structure to “pull” fluid againstan opposing force, such as gravity or against affinity for fluid ofanother substrate with which the structure is in intimate capillarycontact, can be characterized by the capillary pressure. The capillarypressure can be characterized as the hydrostatic head at which thevertically wicked fluid loading is 50% of the free absorbent capacityunder equilibrium conditions at 31° C. The hydrostatic head isrepresented by a column of fluid (e.g., synthetic menses). The upperlayer 30 can have a capillary pressure of 2 cm to 15 cm.

The open-celled foam disclosed herein can be used in an initiallycompressed state that expands to full volume as a function of wear timeand/or fluid loading. The foam may collapse after an insult of fluid asthe lower layer pulls fluid away from the foam.

FIG. 2 is an enlarged cross section view of the absorbent article 10shown in FIG. 1 having a body-contacting surface 12 and a topsheet 14having an upper surface 32 and lower surface 35 opposite the uppersurface 32. The absorbent article 10 has a liquid impervious backsheet16 joined to the topsheet 14, and an absorbent core 18 disposed betweenthe topsheet 14 and the backsheet 16. The absorbent core 18 has athickness t and a width w. The backsheet 16 has an upper surface 44 anda lower surface 42 opposite the upper surface 44. The absorbent core 18has an absorbent core upper layer 30 and an absorbent core lower layer40. The absorbent core upper layer 30 contains an upper surface 36 and alower surface 38 opposite the upper surface 36. The upper surface 36 ofthe absorbent core upper layer 30 may be in direct contact with thelower surface 35 of the topsheet 14. The absorbent core lower layer 40contains an upper surface 46 and a lower surface 48 opposite the uppersurface 46. The lower surface 38 of the absorbent core upper layer 30 isin contact with the absorbent core lower layer 40 upper surface 46. Thelower surface 48 of the absorbent core lower layer 40 is in contact withthe upper surface 44 of the backsheet. The absorbent article may have anadhesive 82 on the lower surface 42 of the backsheet 16.

FIG. 3 shows a schematic cross section of an absorbent core lower layer40 according to on embodiment of the present invention. The absorbentcore lower layer 40 can have a substrate layer 100, a layer of absorbentpolymer material 110, and a layer of adhesive 120. Typically theadhesive can be a hot melt adhesive. In an embodiment of the presentinvention, the layer of adhesive 120 can be typically for example alayer of fiberized hot melt adhesive 120. The substrate layer 100 canfor example comprise a fibrous material.

The substrate layer 100 comprises a first surface and a second surface.Conventionally, in all the sectional views illustrated in the attacheddrawings the first surface of each layer is meant to correspond to thetop surface, in turn, unless stated otherwise, corresponding to thewearer facing surface of the article 20 incorporating the absorbentcore, while the second surface corresponds to the bottom surface, hencein turn the garment facing surface. At least portions of the firstsurface of the substrate layer 100 are in contact with a layer ofabsorbent polymer material 110. This layer of absorbent polymer material110 comprises a first surface and a second surface, and can be typicallya uniform or non uniform layer, wherein by “uniform” or “non uniform” itis meant that the absorbent polymer material 110 can be distributed overthe substrate layer 100 respectively with uniform or non uniform basisweight over the area interested by the distribution. Conversely, thesecond surface of the layer of absorbent polymer material 110 is in atleast partial contact with the first surface of the substrate layer 100.According to an embodiment of the present invention, the layer ofabsorbent polymer material 110 can also be a discontinuous layer that isa layer typically comprising openings, i.e. areas substantially free ofabsorbent polymer material, which in certain embodiments can betypically completely surrounded by areas comprising absorbent polymermaterial. Typically these openings have a diameter or largest span ofless than 10 mm, or less than 5 mm, or 3 mm, or 2 mm, or 1.5 mm and ofmore than 0.5 mm, or 1 mm. At least portions of the second surface ofthe absorbent polymer material layer 110 are in contact with at leastportions of the first surface of the substrate layer material 100. Thefirst surface of the layer of absorbent polymer material 110 defines acertain height of the layer of absorbent polymer material above thefirst surface of the layer of substrate material 100. When the absorbentpolymer material layer 110 is provided as a non uniform layer, typicallyfor example as a discontinuous layer, at least some portions of thefirst surface of the substrate layer 100 are not covered by absorbentpolymer material 110. The absorbent core 28 further comprises a layer ofadhesive 120, for example typically a hot melt adhesive. This hot meltadhesive 120 serves to at least partially immobilize the absorbentpolymer material 110. According to an embodiment of the presentinvention, the adhesive 120 can be typically a fiberized hot meltadhesive, i.e., being provided in fibres as a fibrous layer.

In a typical embodiment of the present invention the thermoplasticmaterial 120 can be provided as a fibrous layer which is partially incontact with the absorbent polymer material 110 and partially in contactwith the substrate layer 100. In this structure the absorbent polymermaterial layer 110 is provided as a discontinuous layer, a layer offiberized thermoplastic material 120 is laid down onto the layer ofabsorbent polymeric material 110, such that the thermoplastic layer 120is in direct contact with the first surface of the layer of absorbentpolymer material 110, but also in direct contact with the first surfaceof the substrate layer 100, where the substrate layer is not covered bythe absorbent polymeric material 110, i.e. typically in correspondenceof the openings of the discontinuous layer of the polymer material 120.By “direct contact” it is meant that there is no further intermediatecomponent layer between the layer of thermoplastic material 120 and theother respective layer in direct contact thereto, such as for example afurther fibrous layer. It is however not excluded that a furtheradhesive material can be comprised between the layer of thermoplasticmaterial 120 and the optional cover layer 130, when present, or thelayer of absorbent polymer material 110 or, more typically, thesubstrate layer 100, such as for example a supplementary adhesivematerial provided onto the first surface of the substrate layer 100 tofurther stabilize the overlying absorbent polymer material 110. “Directcontact” can hence be considered to mean in this context a directadhesive contact between the layer of thermoplastic material 120 and theother respective layer as explained above. This imparts an essentiallythree-dimensional structure to the fibrous layer of thermoplasticmaterial 120 which in itself is essentially a two-dimensional structureof relatively small thickness (in z-direction), as compared to theextension in x- and y-direction. In other words, the fibrousthermoplastic material layer 120 undulates between the first surface ofthe absorbent polymer material 110 and the first surface of thesubstrate layer 100. The areas where the fibrous thermoplastic material120 is in contact with the substrate layer 100 are the areas of junction140.

Thereby, the thermoplastic material 120 provides spaces to hold theabsorbent polymer material 110 typically towards the substrate layer100, and thereby immobilizes this material. In a further aspect, thethermoplastic material 120 bonds to the substrate 100 and thus affixesthe absorbent polymer material 110 to the substrate 100. Typicalthermoplastic materials will also penetrate into both the absorbentpolymer material 110 and the substrate layer 100, thus providing forfurther immobilization and affixation.

As shown in FIG. 4, the absorbent core upper layer 30 perimeter 66 andthe absorbent core lower layer 40 may not share the same centraltransverse axis. Section one 52 of the upper layer 30 may be locatedover section two 58 of the lower layer 40. The advantage of thisorientation is best understood when understanding the interactionbetween an absorbent article 10 and a woman's body.

Applicants have surprisingly found that using an absorbent core upperlayer 30 that contains less surface area than the lower layer 40 and isplaced in proximity to the pudendal region further leads to improvedreduced wetness on the body. The use of a foam absorbent core upperlayer 30 may also allow for the absorbent article 10 lower layer sectiontwo 58 to be thinner for improved comfort and fit while lower layersection one 56 is larger as the absorbent article expands towards theback without having absorption. The shape of the perimeter 66 of theabsorbent core upper layer 30 may facilitate reduced bunching due to theshape of the continuous portion 62 or the combined effect of thediscontinuous portions 64. Applicants have found that shaping theabsorbent core upper layer 30 to match a women's pudendal region interms of area can allow for improved matching to the natural shape ofthe body while not sacrificing absorbency. Further, the orientationwherein the upper layer 30 section one 52 of the absorbent core islocated on top of the lower layer 40 section two 58 can allow for alarger general surface area in the back section of the absorbent article10 to protect from leaks and undergarment soiling that may not come indirect contact with the pudendal region.

Applicants have also surprisingly found that by manipulating the shapeof the absorbent core upper layer 30 and the absorbent core lower layer40, one can create an absorbent article that has uniform absorptivecapacity for each transverse slice moving up the longitudinal axis L ofthe absorbent article for greater than 80% of the absorbent article 10while improving the comfort and fit of the absorbent article 10. Thiscan be done using an absorbent core upper layer 30 continuous portion 62or by using multiple absorbent core upper layer 30 discontinuousportions 64. Traditionally, absorbent articles have to trade off betweencomfort and absorbency. This is because the increasing absorbency oftenmeans increasing width or thickness of the absorbent article 10.Applicants have found that by manipulating the shape of the absorbentcore upper layer 30 and the absorbent core lower layer 40, the absorbentarticle 10 can have improved comfort and fit without having to sacrificeabsorbency. The absorbent core upper layer 30 is manipulated to becomewider as the absorbent core lower layer 40 is manipulated to becomenarrower while still being wider than the absorbent core upper layer 30.This improves comfort and fit which may depend on the total width andthickness of the absorbent article while maintaining the preferred levelof absorbency. Applicant's absorbent article 10 maintains a minimumlevel of absorbency throughout 80% or greater of the longitudinaldistance of the absorbent article 10 while improving the comfort and fitto the body.

Additionally, Applicants have discovered that the proposed use of anabsorbent core 18 having two layers significantly reduces bunching whilein use. Bunching occurs when the absorbent article 10 folds upon itselfthereby impacting absorption and comfort. Applicants have found that theabsorbent core upper layer 30 acts like a memory-like foam that molds tothe curves of the body while the absorbent core lower layer 40 fits thedesign of the undergarment. This reduces the gap between the absorbentarticle and the body thereby reducing bunching.

The dimensions and values disclosed herein are not to be understood asbeing strictly limited to the exact numerical values recited. Instead,unless otherwise specified, each such dimension is intended to mean boththe recited value and a functionally equivalent range surrounding thatvalue. For example, a dimension disclosed as “40 mm” is intended to mean“about 40 mm.”

Every document cited herein, including any cross referenced or relatedpatent or application, is hereby incorporated herein by reference in itsentirety unless expressly excluded or otherwise limited. The citation ofany document is not an admission that it is prior art with respect toany invention disclosed or claimed herein or that it alone, or in anycombination with any other reference or references, teaches, suggests ordiscloses any such invention. Further, to the extent that any meaning ordefinition of a term in this document conflicts with any meaning ordefinition of the same term in a document incorporated by reference, themeaning or definition assigned to that term in this document shallgovern.

While particular embodiments of the present invention have beenillustrated and described, it would be obvious to those skilled in theart that various other changes and modifications can be made withoutdeparting from the spirit and scope of the invention. It is thereforeintended to cover in the appended claims all such changes andmodifications that are within the scope of this invention.

1.-20. (canceled)
 21. An absorbent article, the absorbent articlecomprising: a topsheet having a body contacting surface and a lowersurface opposite the body contacting surface; a backsheet joined to thetopsheet; and an absorbent core disposed between the topsheet and thebacksheet, wherein the absorbent core comprises an upper layercomprising an upper surface having an upper layer surface area, and alower surface opposite the upper surface, and a lower layer; the upperlayer comprising an open celled foam and the lower layer comprising afibrous network and superabsorbent polymer; wherein the upper layer hasa transverse axis, the upper layer transverse axis dividing the upperlayer surface area into a section one surface area and a section twosurface area; wherein the section one surface area is at least 5%greater than the section two surface area.
 22. The absorbent article ofclaim 21 wherein the topsheet comprises apertures.
 23. The absorbentarticle of claim 21 wherein the upper layer comprises apertures.
 24. Theabsorbent article of claim 21 wherein the absorbent article has a firsttransverse axis and the upper layer has a second transverse axis, andthe second transverse axis is 5 cm or less from the first transverseaxis.
 25. The absorbent article of claim 21 wherein the open celled foamcomprises polyurethane.
 26. The absorbent article of claim 21 whereinthe open celled foam comprises a HIPE foam.
 27. The absorbent article ofclaim 21 wherein the lower layer has a lower layer upper surface havinga lower layer surface area, and the upper layer surface area is nogreater than 95% of the lower layer surface area.
 28. The absorbentarticle of claim 21 wherein the open celled foam has a thickness betweenabout 0.8 mm to about 3.5 mm.
 29. The absorbent article of claim 21wherein the absorbent core has a total thickness between about 0.8 mm toabout 18 mm.